An East Harlem soccer field has been closed after elevated lead levels were detected in the synthetic turf installed five years ago, park officials said Monday.

The exact cause of the lead contamination at Thomas Jefferson Park, at First Ave. and E. 113th St., is not known, according to Parks Commissioner Adrian Benepe.

But Geoffrey Croft, a park advocate and frequent critic, blamed the lead contamination on the city's use of a type of synthetic turf that includes a cushion of pulverized tires, known as crumb-rubber infill.

The field was fenced in and closed Wednesday, although a running track around it remains open. The field will be reopened when the turf is removed and replaced.